There have been known printers including line-type ejection heads. Some of the known line-type ejection heads includes a plurality of head units positioned along a width direction of a recording medium.
In such an ejection head, one head unit partially overlaps another head unit in a conveyance direction. If nozzles of the one head unit are misaligned with their corresponding nozzles of the another head unit at the overlap area, a streak (e.g., a white streak or a black streak) tends to occur in an image formed by the nozzles positioned at the overlap area. In order to solve this problem, various methods for reducing occurrence of the streak have been proposed.
In one example, an ejection head includes a plurality of head units. The head units are disposed such that printable ranges of adjacent two of the head units in a width direction of the recording medium partially overlap each other. A nozzle pitch in one of the adjacent head units is greater than a nozzle pitch in the other of the adjacent head units. In this ejection head, at an overlap area where the adjacent head units partially overlap each other, particular nozzles of the one head unit are aligned with particular nozzles of the other head unit. Thus, the nozzles of the one and other head units are appropriately used depending on the locations with respect to the particular nozzles (i.e., a boundary). That is, on one side relative to the boundary, the one head unit is caused to eject ink from one or more of the nozzles thereof. On the other side relative to the boundary, the other head unit is caused to eject ink from one or more of the nozzles thereof. Such an ink ejection manner may reduce occurrence of the streak in an image formed by the nozzles positioned at the overlap area.
In another example, an ejection head includes a plurality of head units. The head units are disposed such that printable ranges of adjacent two of the head units partially overlap each other. At the overlap area of the ejection head, ink droplets are ejected from nozzles of both of the adjacent head units. At another area of the ejection head, ink droplets are ejected from nozzles of the one or the other of the adjacent head units. Ink droplets ejected from the nozzles of each of the adjacent head units positioned at the overlap area dispersedly land on a recording medium to form a joint of images formed by the nozzles of the one head unit and the nozzles of the other head unit, respectively. Therefore, nozzle misalignment between the head units may less affect the print result.